ADD IT UP: Tony Abbott and Kevin Rudd in a faceoff. Source: The Courier-Mail

IS IT possible to calculate the effect of a Rudd return on Labor's vote?

Julia Gillard's supporters hope not, preferring to think the former PM's promise not to challenge her before the election - nor allow himself to be drafted for the top job - has finally put leadership speculation to bed.

If we were talking about any other politician, it probably would.

But we're talking about one Kevin Michael Rudd - a man who clearly hates to leave any job unfinished and for whom the word wallflower means nothing.

With apologies to Shakespeare, many a voter would today say Kevin doth protest too much, methinks.

Like Queen Gertrude, I suspect the former PM has overcooked his denials.

The sceptic in me can't help but wonder why Rudd has returned to the Sunrise television program, or tweeted about grandfatherly virtues, or taken a swing at Treasurer Wayne Swan's mining tax.

Even his postponement of a potentially scene-stealing Adelaide street walk will be read as a calculated leadership move.

I have no doubt that Rudd is genuine when he says he will not force a challenge, but I can't believe he'd resist being drafted if the leadership were offered on a platter.

While there's virtually no chance of that, Gillard supporters must still be worried by the weekend's Galaxy poll that suggested Labor's last card - women's hitherto dislike of Tony Abbott - has turned out to be a joker.

Galaxy found women voters were now evenly divided in terms of whom they trusted, Gillard or Abbott.

It seems that Abbott's gender "problem" has finally been laid to rest, or at least close to it.

Gillard's wavering supporters must now be second guessing the mathematics of a Rudd revival and weighing up whether the Queensland Kid will help them retain their marginal seats.

But picking an election winner seven months out is risky enough, even when the opinion polls have been as consistently stark as those dividing Labor and the Coalition.

Throw in the unknown variable of potential leadership challenges and it's nigh on impossible.

But that won't stop us having a bit of fun with the numbers and I've looked to previous pre-election leadership speculation for some guidance.

In early 1995, for example, when John Howard was about to topple the hapless Alexander Downer, Howard - not yet opposition leader - was polling 49 per cent as preferred PM to the incumbent Paul Keating's 43 per cent, a six-point margin.

On top of this was the Coalition's nine-point lead over Labor, 47 to 38 per cent.

Together, that equalled a 15-point Coalition advantage over Labor, or 7.5 points if averaged over the two criteria.

Given the Coalition under Howard gained 28 seats at its easy 1996 election victory, we can conclude that each point of the Howard advantage was worth an extra 3.7 seats for the Liberal and National parties.

Let's apply that matrix to 2013.

The most recent polling from late last year indicates that Rudd leads Abbott as preferred PM by a whopping 19 points.

But this is tempered by the fact the Government's primary vote trails the Opposition's by an equally staggering 16 points, 32 to 48 per cent.

Together, that pegs the Rudd advantage at just three net points, or a mean of just 1.5 per cent over two criteria. Multiply 1.5 by 3.7 seats and we can surmise a Rudd-led Labor could make a net gain of five or six seats, bringing the Government's total to 77 or 78 - a tiny but certain majority.

Will this happen? Probably not. But the speculation is fun.

And, as Howard said, politics is all about arithmetic.

Dr Paul Williams is a Griffith University School of Humanities senior lecturer.

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